Winter Storm Watch: Snow/Ice Likely Later Thursday

January 31, 2017

5pm Tuesday…

The NWS has issued a Winter Storm Watch for much of Western Oregon between the Coast/Cascade Ranges for Thursday and Friday.

markwarningswinter-wx

That means snow and/or freezing rain is POSSIBLE during this period but some of us may not get it, or get much of it.

We’re still two days away, but models have come into much better agreement on the general sequence of events the next 4 days:

HIGHLIGHTS

  • Wednesday will be colder with a very strong east wind spreading out across the metro area
  • Wednesday should be a dry day, or mainly dry.  Possibly a flurry/sprinkle in the afternoon that WILL NOT AFFECT ROADS.
  • Thursday AM should be dry as well for a clear AM commute.
  • At some point Thursday afternoon or evening, snow will spread north across Western Oregon and up into SW Washington.  Timing is TBD since we’re still 2 days away.
  • First guess (still 2 days away!) is 1-2″ snow for many of us in the western valleys before a transition to freezing rain by Friday AM.  If the transition takes longer?  More snow, less freezing rain.
  • During the day Friday, freezing rain is likely at times, but it’ll become confined to near the Columbia River Gorge (central/east Portland metro area) as temperatures rise above freezing in most other locations.
  • It’s possible that Friday afternoon many of us will see mainly wet roads south/west/north metro away from the Gorge.  This happened during the last two freezing rain events when we thought a large area would see freezing rain and instead it was confined to the central/east metro area.
  • A warming southerly wind late Friday night or early Saturday ends the freezing rain threat outside of the Gorge at that time.

ROADS/SCHOOLS

I see either Thursday evening and Friday morning commutes being a possible big issue anywhere in the valleys.  Friday could be a no-school day for many.  It could possibly still be very icy in parts of the metro area Friday evening too.  Again, we’ve got another 24-36 hours to fine-tune the forecast

 

WEATHER GEEK CHAT

Here we go again, hopefully for the last time this winter.  It was nice to see models come together pretty well on last night’s runs, and the same thing through this morning/midday runs too.  No model is showing any sort of significant snow now tomorrow through Thursday AM.  After checking several model’s thermal profile up through the atmosphere, I’m becoming convinced this will be more of a freezing rain “storm” than a snowstorm for most of us.  I think just about everything I checked shows that warming occurs overhead before sunrise Friday, so all of Friday’s precip will be in a liquid form.  That’s at least while falling.  Of course if surface temps are below freezing then you get the ice glazing which we’ve seen 3 times already this winter in the valleys!  Check out snow forecast from the GFS:

gfs_snow_fridaypm

The ECMWF

ecmwf_snow

and the WRF-GFS

wrf_snow_fridaypm

None show more than 2″ anywhere in the western valleys.  That’s due to warmer air coming in overhead…not “warm”, but warmer.  Then the next question has been “how cold will the air mass be that moves in on the east wind?”  I see several hints that it won’t be as cold as previous events in January.  The result could be that it’ll be easier to get temps above freezing over a larger area west of the Cascades during the daytime Friday, even with the easterly flow continuing through the Gorge.

I know we are all focused on snow and freezing rain, but I need to mention the strong wind tomorrow too.  Check out the cross-section from the WRF-GFS for the next 3 days.

kpdx-th

The solid wind barbs represent 50kts and each little barb is 10 kts.  So from tomorrow morning through Thursday evening easterly wind is forecast to exceed 60 mph over our heads…up around 2,000′.  Some of this strong wind will surface as gusts around 40-50 mph.  Of course this means we’ll see a few limbs/trees come down, especially across the east side of the metro area.  Since we’ve already seen wind this strong this winter I doubt we’ll see widespread power outages.  But regardless, it’s going to be a gray and chilly afternoon Wednesday.  It’ll be a big reminder that winter isn’t finished yet!

Chief Meteorologist Mark Nelsen

 


Snow/Ice Possible Later This Week

January 30, 2017

4pm Monday…

Late Evening Edit:  A few new thoughts at 10pm with all evening models in nowupdates in red

It’s been a very gloomy day out there with low clouds hanging over most of the metro area.  The good news is Tuesday will be a much brighter day; I expect clouds to break up to partly to mostly sunny skies in the wake of a cold front passing through the region.  The air coming in tomorrow is cooler and drier, thus the increasing sunshine.

Of course what we all care about is that Wednesday-Friday time period I mentioned in the posting Sunday night:

THE BIG PICTURE

The 2nd half of this week we’ll be in a “conflict zone” in the Pacific Northwest where the colder air from the north moves down under milder/moist air above.  That “zone” seems to want to hang out somewhere near the Oregon/Washington border Wednesday through Friday according to most models.  But details are very uncertain through that whole 3 day period and I don’t have a lot more info to give you this afternoon…we’re just going to have to wait until we get closer (Tuesday) to see if we can get some better forecast agreement among the models.  But I can give you a few more tidbits this afternoon that might help with you late week decision-making…

HIGH CONFIDENCE ON THESE DETAILS:

  1. A cold east wind arrives in the Gorge tomorrow and tomorrow night.  It’ll blow quite hard Wednesday-Friday in the Gorge and east metro
  2. Expect high temperatures mainly 32-38 in the metro area Wednesday-Friday
  3. Temperatures remain at/below freezing Wednesday-Friday in the Gorge.
  4. At some point we’re going to see sticking snow and/or freezing rain in at least portions of the metro area during this period.
  5. The Gorge turns snowy/icy again with a little snow late tonight/Tuesday AM, then quite a bit likely Thursday/Friday.

LOW CONFIDENCE:

  1. Will we actually see snow sticking in the metro area Wednesday?  Possibly, but as of now most models are mainly dry for that day.  This could change. (10pm update)  All models except our RPM are pretty much dry Wednesday.  I’ve taken the chance of anything other than flurries out of the Wednesday/Wednesday night forecast.
  2. How much moisture Thursday/Friday?  Some models are mainly dry through at least midday Thursday and then light freezing rain Thursday night/Friday AM.  Others have more widespread snow Thursday before a changeover.  I’m sticking with a later arrival (sometime Thursday) for now. (10pm update)  Definitely a later Thursday & Friday event showing up now.  Thursday might even be dry to start.
  3. The cold air mass over us Wednesday-Friday isn’t nearly as cold as what we saw in the first half of January.  That means it’s possible even IF we get a bunch of precipitation Thursday/Friday, some areas could be above freezing west of the Cascades = less frozen precip.  Another reason the forecast is very tricky.

Will there be school closures?  Not through Wednesday, but we’ll see about Thursday & Friday.  (10pm update)  It’s possible no road issues until later Thursday

Note the preferred ECMWF model is quite dry and/or not quite cold enough all the way through Friday for most areas west of the Cascades:

ecmwf_snow_fridaymidday

While the 18z GFS has a dusting to an inch or so.  gfs_18zsnow

The 12z WRF-GFS is slightly snowier.

wrf_snow_12z

Our RPM is similar with very light snow totals.  But it also thinks it’s above freezing even in the metro area all the way through Thursday midday.  That’s unlikely:

rpm_snowaccum

The big message here is that as of this moment no models are showing a huge snowstorm or major ice storm in the western valleys.  But we all remember the January 10th snowstorm though when all that moisture appeared out of nowhere!  A good reason to keep an eye on trends in modeling and satellite imagery of course.

Stay Tuned!

Chief Meteorologist Mark Nelsen


January: Coldest Month Since My High School Years

January 29, 2017

11pm Sunday…

Since we only have 2 days left this month we have a pretty good idea where January will end up in the history books

markjanuarycoldmonthpdx

As of tonight, the 33.2 degree average temperature makes January 2017 the coldest month in Portland since December 1985!  That was halfway through my junior year in high school…a long time ago in a county far, far (80 miles) away.  That month we had high pressure centered over the Pacific Northwest much of the month with snow-covered terrain east of the Cascades the whole time.  Cold east wind blew much of the month through the Gorge…sound familiar?

This will also be the 7th or 8th coldest month on record at PDX.  Those airport weather records go back to 1939.

What’s Ahead?

It appears we have one more brush with cold/snow/ice this week as February arrives.    Once again the Alaska upper-level ridge is trying to rise again.  It did that in early/mid December and early/mid January.  That shoves cold air to its east (over Western Canada) to the south toward and into the Pacific Northwest.  There will be a “conflict zone” in the Pacific Northwest where the colder air from the north moves down under milder/moist air above.  That “zone” seems to want to hang out somewhere near the Oregon/Washington border Wednesday through Friday according to most models.

I’m VERY confident we have a chilly east wind back in the Gorge and east metro Wednesday-Friday.  I’m FAR LESS confident about the depth & intensity of the cold air and how much moisture rides over it Wednesday-Friday.  For that reason I have very few details for now.

marksnowsetup2_coldfromeast

This is just a brief posting to answer a few basic questions; of course I’ll have lots more details in the next few days

HIGHLIGHTS

  • As of this moment I think we’re “safe” from any travel issues west of the Cascades (due to snow/ice) through Wednesday afternoon at least.
  • Wednesday-Friday will be a cold three days with a gusty east wind blowing in the usual Gorge and Gorge-influenced areas (you know who you are!)
  • Most models have very little moisture available for snow or freezing rain west of the Cascades until at least sometime Thursday or Thursday evening.
  • There is no need to cancel plans or have any sort of “grocery-store freak out” tomorrow or Tuesday.
  • Everything points to quite a bit of warming next weekend west of the Cascades with very mild weather next week, we are not entering a many days-long freeze
  • The airmass moving into our area is not as cold as the one over us the first half of January
  • If you live in the Gorge (especially central/east) it’s very likely another snow/ice episode is coming at some point Wednesday night-Saturday.  Temps near/below freezing during that time.

 

Maybe most important, as of now I don’t see a similar setup for a road fiasco like early January.  By that I mean the failure of local transportation agencies to clear roads of solid snow/ice well after the event.  This isn’t a “snow, then hard freeze for a bunch of days” setup like the first half of January.  Even if we get snow/ice it will go away within a short time (hours to a day or two).

Stay tuned!

Chief Meteorologist Mark Nelsen


Today: 317 Years Since Last Subduction Zone Quake

January 26, 2017

8am Thursday…

The weather is quite slow again today with areas of morning fog/clouds leading to at least partly cloudy conditions this afternoon.  A little more easterly flow Friday through Sunday SHOULD give us more sunshine.  We’ll see how that works.  The next chance for a real soaking isn’t going to be until February!  That would be next Wednesday of course.

As of Wednesday, January is the 5th coldest month on record here in Portland.  We still have 6 relatively mild days to go, but we could easily end up with the coldest month since 1990 here in Portland and one of the top 10 coldest months!

capture

On another note, today is the anniversary of the last great Cascadia Subduction Zone earthquake.  It was in the evening, January 26th, 1700.  Geologists tell us it was likely at least a 9.0 magnitude quake just offshore.

How do geologists know?

If you have some time take a look at this info on the Orphan Tsunami of 1700 .  I think it’s fascinating reading, but of course I find almost anything scientific to be fascinating.  It’s a paper written by Brian Atwater  and others about the clues to a massive West Coast earthquake, summarized in the graphic below

capture2

Some have theorized the massive Bonneville Landslide and the resulting “Bridge of the Gods” in the central Columbia River Gorge could have been triggered/formed by the big quake, but it appears maybe it is too old for that to be the case.  Great reading again just on the Wikipedia link.

Enjoy the weekend!

Chief Meteorologist Mark Nelsen


A Quiet Sunday Evening

January 22, 2017

It is REAL quiet in the weather world this evening.  After tons of weather fun/craziness to talk about more or less since the first week of December, things are much calmer now.

I don’t see any stormy weather, flooding, cold spell, or high winds in the next week.  It appears January is going to go out with a whimper compared to the first two weeks.  The snow and ice are ever so slowly melting in the Gorge.  I see for the first time in 2017 The Dalles has made it to 40 degrees today!

marktempthedalles_last12days

That’s a good 21 degrees warmer than last Sunday’s high of 20.  Wow, that was a cold 6 day stretch below 24 degrees for you folks.  Here in Portland we were in the mid 40s near the Columbia River, but up around 50 in areas removed from that cool easterly wind drift.

Today a big storm rotated up along the Oregon Coast, but with the surface low so far offshore we just saw light easterly wind.  Farther south in California it was a much different story.  Huge rain totals soaked the whole Los Angeles area.  Lots of flooding down there

plot_rain_california_autoplot

Check out the “water year” rain totals along the West Coast…

markwestcoastrain_california

EVERYONE is getting in on the precipitation this year, which has pretty much erased drought along the West Coast.

droughtmonitor_autoplot

It seems like the Drought Monitor graphic usually runs behind a few weeks, so we’ll see if that southern part of California improves.

 

The big storm that soaked California today may give the southern half of Oregon a few scattered showers again Monday, but for those of us north of Salem/Bend, Monday is looking mainly or all dry.  We’ll go partly cloudy in the afternoon.  Tuesday looks similar and then a very weak weather system runs into a developing ridge of high pressure late Wednesday and that MIGHT give us a shower late in the day or Wednesday night.

Colder easterly wind develops later Thursday through Saturday as we go into a typical wintertime inversion pattern.  That’s warming in the mountains and chilly valleys.

Enjoy the break from the weather this week!

Chief Meteorologist Mark Nelsen

 


Warm South Wind Has Arrived!

January 18, 2017

9:30pm Wednesday…

Portland suddenly jumped to 46 degrees this hour as a warming “Chinook” wind arrived.  The same thing happened in Troutdale and Corbett as a cold front passed by.  That front mixed out the cold air lingering at the far west end of the Gorge.  In fact Troutdale is the warmest location in the ENTIRE metro area this hour!

plot_temps_metro

By the way, the term “Chinook wind” was first used along the Pacific Coast, then the term was adapted to use in the Rockies and Great Plains to describe the warming west wind there in wintertime.  It refers to a sudden warming after a cold spell in winter.  That pretty much describes this evening.

But a south wind won’t make it far into the west-east oriented Columbia River Gorge.  Temperatures will only slowly moderate 3-5 degrees above freezing from Bonneville to The Dalles Thursday.  The cooler east wind does return on Friday and I don’t see a setup in the next 5 days that would push a warm wind all the way through the Gorge.

The NWS has dropped the Ice Storm Warning in the Gorge this evening due to precipitation tapering off quickly now that the cold front has moved by.

This ice storm is the most destructive I’ve seen in the central Gorge with 1-2″ solid ice accumulation from Troutdale to Stevenson/Cascade Locks area.  From what I hear the damage is especially extensive in Skamania county and around Cascade Locks to Dodson.  Hood River was spared the thickest glazing due to part of the storm seeing ice pellets instead of liquid rain.  I-84 has been closed now for about 30 hours and will remain that way until at least sunrise.  There is beauty in the ice though…take a look at some of the pics, which I’ve put into a gallery below:




I’m so glad we ended up slightly too warm in the east metro area or we could have seen something similar in Gresham, Fairview, & East Portland.

Tomorrow’s weather will be uneventful with scattered showers and maybe even a few sunbreaks.  Enjoy the slowdown.

Chief Meteorologist Mark Nelsen


Ice Storm Near & In Gorge Tonight

January 17, 2017

10:15pm…

At least the forecast ice thickness panned out, but just in a much smaller part of the metro area.  Check out how thick the ice is!

markfreezingrain_icetotalssofarpdx

…An inch of freezing rain in just about 8 hours in Troutdale.  There could easily be 1/2″ additional before temps rise much more by sunrise.

Farther into the Gorge the ice storm continues through Wednesday, likely going slightly above freezing at the west end though.

markfreezingrain_gorge

Chief Meteorologist Mark Nelsen